Re: NANFA-- Louisiana sinking and other thoughts

Bruce Stallsmith (
Wed, 05 Mar 2003 13:20:32 -0500

Todd, your line of analysis seems to be pretty good. From what I understand,
the salinity of the world's oceans hasn't much changed since the beginning
of the Paleozoic 'bout 543 million years ago even with dramatic swings in
sea level. The mass extinction at the end of the Cretaceous eliminated about
20% of animal families, based on the work of Raup and Jablonski, and the
species percentage was somewhat higher at 40% (if I remember correctly, the
reference isn't in front of me). Interestingly, as well as wiping out the
dinosaurs, the ensuing ecological cataclysm following the apparent asteroid
impact (involving the world's forests all burning very quickly and the
atmosphere being full of dust and soot for centuries afterwards) was a
severe enough event to lower temporarily the pH of the world's oceans to
about 6.8, causing a mass extinction of marine plankton especially diatoms.
And terrestrial ecosystems were dominated by fern forests for several
million years, as the environment recovered. But that's another story...

--Bruce Stallsmith
Huntsville, AL, US of A

>The exclamation point on all of this happens at the end of the Cretaceous.
>All thru these changes life adapted, and background extinction remained
>constant. It wasn't until the end when some cataclysmic event happened (I
>think this is the Gulf of Mexico Impact?) that caused a mass extinction.
>I'm unfortunately not seeing what the total losses were in biodiversity...
>Perhaps someone else has that information more readily available.
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